Authors:M. Hyvönen-Dabek, J. Räisänen, and J. Dabek
A simple proton beam (PIXE) arrangement developed for a low energy accelerator was used for the determination of absolute
concentrations of nine trace elements in human bone samples. The 2.4 MeV proton beam was externalized through a thin (2 μm)
aluminiummylar foil. Using an air cooling system, the foil withstood a high current (0.5–1 μA) for a long time. The samples
were cooled to prevent damage and volatilization of elements. The induced X-rays were detected with a Si(Li) detector and
the external beam was monitored with a second detector, measuring K X-rays induced in atmospheric argon. The mean (SD) trace
element levels (ppm) measured in dense bone by comparison with hydroxyapatite/standard mixtures were: Cr<2.0, Mn<2.3, Fe 7.58
(1.55), Ni<2.4, Cu 3.58 (2.16), Zn 144 (27), Pb 12.2 (2.5), Br 12.4 (5.5) and Sr 47.7 (14.3). The detection limits for these
elements achieved in this work were about 1 ppm when rather short measuring times (∼10 min) were used. The coefficient of
variation of a single measurement, e.g. for Zn, was 3–4%. Because of the slow turnover of dense bone, such measurements provide
a means of monitoring long term trace element exposure.
Authors:T. Kupila-Rantala, M. Hyvönen-Dabek, J. Dabek, and J. Räisänen
Proton-induced gamma-ray emission (PIGE) analysis has been applied to the determination of total nitrogen concentration of blood sera from hospital patients. Both the reaction14N(p,p
)14N,E= =2313 keV, and the reaction15N(p,
)12C,E=4439 keV, have been used. From 37 patients, the range of the nitrogen concentrations obtained was 9.54–16.3 g/l with a mean of 12.0 g/l. The corresponding total protein concentrations varied between 59 and 96 g/l, measured in a clinical laboratory autoanalyser using the biuret method. The range of the albumin concentrations was 29–46 g/l. The nitrogen concentrations correlated well with the total protein concentrations (r=0.802). The multiple correlation of nitrogen versus (albumin+(total protein-albumin)) gives a coefficient of 0.175 for albumin and 0.161 for total protein-albumin. The results agree with expectations and support the potential usefulness of the rapid PIGE method for medical studies.
The method of proton-induced X-ray emission (or PIXE) analysis has been investigated with reference to the study of minor
and trace elements in biological tissue. Methods of specimen preparation have been investigated, and optimum instrumental
conditions arrived at. The lower limits of detection for lead and zinc in blood have been investigated and have been found
to be approximately 0.3 and 0.1 ppm for lead and zinc respectively, for a proton energy of 2.5 MeV. The concentrations of
copper, zinc and iron have been studied in normal and diseased human liver tissue. In cirrhotic tissue the copper levels are
substantially raised. We note also a diminution in liver iron in a case of alcoholic cirrhosis associated with clinical anaemia;
and a blood zinc deficiency in primary biliary cirrhosis. The results are discussed in relation to existing work.
Kinetics of oxidation of Fe-Cr steel containing 25 wt.-percent Cr was studied as a function of temperature (1023–1173 K) for
up to 480 h in flowing air, which corresponds to SOFC cathode environment operating conditions. The oxidation process was
found to be a parabolic, suggesting that the diffusion of ionic defects in the scale is the slowest, rate determining step
and it occurs predominantly by short-circuit diffusion paths. Comparison of the determined activation energy of oxidation
of the studied steel with literature data indicates that at 1098–1173 K the chromia scale grows by the outward solid-state
diffusion of chromium interstitials, whereas at 1023–1098 K — through a significant contribution of counter-current oxygen/chromium
diffusion along Cr2O3 grain boundaries. The oxide scales were composed mainly of Cr2O3 with a continuous thin Mn1.5Cr1.5O4 spinel layer on top of the chromia scale. The oxidation test results on Fe-25Cr steel demonstrate the applicability of the
commercial type DIN 50049 stainless steel as interconnect for SOFC.
Authors:Z. Grzesik, S. Mrowec, T. Walec, and J. Dabek
A novel microthermogravimetric apparatus to study the kinetics of metal sulphur reactions and transport properties of transition
metal sulphides has been described. The main feature of this arrangement includes the application of the carrier gas for sulphur
vapour transportation and the protection of the balance chamber from sulphur attack. As a consequence, the helix balance could
have been replaced by an automatic electronic microbalance and the accuracy of the mass change measurements increased more
than two orders of magnitude, up to 10–7 g. The application of two liquid sulphur reservoirs created very stable, strictly defined reaction conditions, and enabled
to make rapid changes of sulphur partial pressure in the reaction chamber. It has been demonstrated that all these innovations
make it possible to study not only the kinetics of very slow sulphidation processes but also to determine deviations from
stoichiometry and defect mobility in transition metal sulphides.
Authors:J. Dabek, D. Vartsky, P. Dykes, J. Hardwicke, B. Thomas, J. Fremlin, and H. James
Whole body nitrogen has been measured absolutely in male volunteers and patients by in-vivo neutron activation analysis using
whole body hydrogen as an internal standard. The 10.8 MeV and 2.2 MeV prompt gamma rays from nitrogen and hydrogen respectively
give a result reproducible to 4% for a dose of 100 mRem. Whole body potassium measured by whole body counting natural40K and whole body nitrogen have been correlated in normal adult males and patients. In the normals the correlation coefficient
was 0.96 with coefficient of variation 4%. In the patients these parameters were 0.92 and 8% in 140 measurements. The ratio
of N/K increased significantly as the degree of clinical wasting progressed.
Authors:D. Vartsky, W. Prestwich, B. Thomas, J. Dabek, D. Chettle, J. Fremlin, and K. Stammers
The previously established technique of analysis of neutron capture γ-rays for the determination of nitrogen in-vivo has been
modified to make estimates of absolute quantities of nitrogen mass. Hydrogen is used as an internal standard and the nitrogen
mass is determined from the observed ratio of nitrogen to hydrogen counts, together with the hydrogen mass, estimated from
body parameters. Phantom and cadaver studies indicate that nitrogen mass can be estimated to ±4% or better by this means.